The present invention relates to a liquid-tight packing container provided with a tear-up opening arrangement of the type which is manufactured from a plane packing material web or a plane packing material sheet by folding so as to form a closed hollow body. At least one side wall of the container is provided with a sealing fin projecting from the side wall of the packing container, which extends over the side wall and up to the apex of a double-walled triangular lug connected with the side wall. The lug is formed during the folding and is intended to form a pouring spout for the decanting of the contents enclosed in the packing container when the packing container has been opened.
The invention also relates to the manufacture of the abovementioned packing container.
Liquid goods, such as e.g. milk, are packed and distributed at the present time almost exclusively in non-returnable packages which are manufactured from plastics or plastic-coated paper. The latter is more common, since a packing material which consists of a combination of paper and plastics will be cheaper than a wholly plastic package and will be more acceptable from an environmental point of view. In accordance with modern principles of packaging, the packin material is supplied in the form of a web consisting of plastic-coated paper. The web can be wound up on a magazine roll to facilitate transport and handling, and also to improve hygiene since the actual packing surface is protected in rolled-up condition against dirt, moisture and external influences. The formation of the packages can be realized so that the said web is folded to a tube by joining together the longitudinal edges of the web through combining the plastic layers in the contact zones by surface melting. The tube thus formed is filled with the intended contents and divided up along narrow transverse sealing zones situated at a distance from each other along the longitudinal axis of the tube. Thereupon the packing units formed are separated by cuts in the transverse sealing zones and shaped by folding to their final package form with the help of folding lines, so-called crease-lines, provided beforehand on the packing material web.
Packages of the abovementioned type can be manufactured in high-speed packing machines and in a very hygienic manner, since the side of the packing material which is intended to form the inside of the packing container is exposed only to a very small degree, and it has been found possible, with the help of the packing technique, to manufacture wholly aseptic packages by sterilizing the inside of the packing material web before or in connection with the tube formation. However, it is a problem to arrange a readily functioning opening for the packing container, since an opening direction entails a weakening of the packing material, which means that such a weakened opening direction may easily bring about leakages, because the opening opens up during handling, for example, in connection with transport. A variety of different opening arrangements has been suggested and used, and in the majority of cases these consist of a tearing perforation, which penetrates the paper layer but not the plastic layer, and is arranged along a defined tearing length. As mentioned above, such tearing perforations have to be realized as a compromise between openability and tightness demands, and great demands on tolerances are made in the perforating operation, since the plastic layer may not be damaged. Among other things it has also been suggested to pierce fully through the packing material with a perforation or cut line, which perforation or cut line is restored after the punching operation with the help of a thin plastic strip which is firmly welded over the punching region against the plastic-coated inside of the packing material. In many cases these opening arrangements have proved to function satisfactorily, but is is imperative that adhesion should be very good right up to the cut edge, since otherwise the inner plastic strip, which is constituted of plastic material, will be stretched and drawn out in a rubberlike manner which brings about difficulties during the opening operation.
The present invention, however, provides a solution to the problem and relates to an opening arrangement in which the packing material forming the packing container is pierced through along a line situated alongside or in the vicinity of the base line of the sealing fin on both sides of the sealing fin, and which extends from the apex of the said triangular lug to a point situated on the said side wall. The pierced portion of the packing material as a whole is covered by a plastic strip which is fixed in liquid-tight manner to the side of the packing material which forms the inside of the packing container. The plastic strip is strongly molecular-oriented in its longitudinal direction, and parts of the plastic strip are attached to one another and fixed in the said sealing fin.
Hence the principle, known in itself, is used that plastic material can be orientation-stretched and that the tearability in the direction of orientation is greatly improved whilst tearability in transverse direction is diminished to the same degree.